Field of the Invention
The present invention is broadly concerned with improved, high capacity die assemblies, the combination of such assemblies with food or feed extruders, and corresponding methods. More particularly, the invention is concerned with such die assemblies including a plurality of structurally distinct, tubular die components, each having wall structure defining an outwardly diverging tubular chamber with an outboard die plate; a diverging flow diverter element is located within each chamber and has a large diameter end adjacent the die plate and a remote small diameter end. The die assemblies are operable to produce high quality extrudates, such as aquatic feeds, at high production rates
Description of the Prior Art
Many types of foods or feeds are produced using extrusion equipment. Generally speaking, such extruders include an elongated, tubular barrel having one or more elongated, axially rotatable, helically flighted extrusion screws within the barrel. The discharge end of the barrel is equipped with a die having a plurality of restricted orifice die openings therethrough. In use, starting materials are fed into the barrel and are subjected to increasing levels of pressure, temperature, and shear within the barrel, and are ultimately extruded through the die.
In the production of certain types of aquatic feeds known as “micro feeds,” the outlet die has relatively small through openings to generate thin, needle-like extrudates. It has been found that production of these micro feeds is often limited by the amount of surface area on the die. Thus, while a given extruder may normally be able to produce high quantities of product, when used to produce micro feeds, the production capacity of the extruder is severely limited. Indeed, in some instances, micro feed production is limited to approximately one-half the rated capacity of the extruder.
A variety of different extruders and die assemblies have been proposed in the past. Representative references include U.S. Pat. Nos. 3,230,902, 3,813,082, 5,171,090, 5,223,296, 5,242,292, 5,540,900, 6,531,077, 7,654,813, and 8,114,454; US Patent Publication No. 2005/0092365; foreign patents JP10191948 and JP11009197; and non-patent literature: “Ring Die Aquatic Feed Pellet Mill” http://www.feed-pellet-mill.com/product/Feed-Pellet-Mill/ring-die-aquatic-feed-pellets-mill.html (Accessed Jun. 30, 2015), and Sprout “Controlled starch cook and bulk density of dry pet food—Is this for real?” http://en.engormix.com/MA-feed-machinery/formulation/articles/controlled-starch-cook-bulk-t236/p0.htm (Accessed Jul. 7, 2015).